package cn.aishua.util;

import android.view.animation.Animation;
import android.view.animation.Transformation;
import android.graphics.Camera;
import android.graphics.Matrix;

/**
 * An animation that rotates the view on the Y axis between two specified angles. This animation
 * also adds a translation on the Z axis (depth) to improve the effect.
 */
public class Rotate3dAnimation
    extends Animation
{
    private final float mFromDegrees;
    private final float mToDegrees;
    private final float mCenterX;
    private final float mCenterY;
    private final float mDepthZ;
    private final boolean mReverse;
    private Camera mCamera;

    /**
     * Creates a new 3D rotation on the Y axis. The rotation is defined by its start angle and its
     * end angle. Both angles are in degrees. The rotation is performed around a center point on the
     * 2D space, definied by a pair of X and Y coordinates, called centerX and centerY. When the
     * animation starts, a translation on the Z axis (depth) is performed. The length of the
     * translation can be specified, as well as whether the translation should be reversed in time.
     * 
     * @param fromDegrees
     *            the start angle of the 3D rotation
     * @param toDegrees
     *            the end angle of the 3D rotation
     * @param centerX
     *            the X center of the 3D rotation
     * @param centerY
     *            the Y center of the 3D rotation
     * @param reverse
     *            true if the translation should be reversed, false otherwise
     */
    public Rotate3dAnimation(float fromDegrees, float toDegrees, float centerX, float centerY, float depthZ,
        boolean reverse)
    {
        mFromDegrees = fromDegrees;
        mToDegrees = toDegrees;
        mCenterX = centerX;
        mCenterY = centerY;
        mDepthZ = depthZ;
        mReverse = reverse;
    }

    @Override
    public void initialize( int width, int height, int parentWidth, int parentHeight )
    {
        super.initialize( width, height, parentWidth, parentHeight );
        mCamera = new Camera();
    }

    @Override
    protected void applyTransformation( float interpolatedTime, Transformation t )
    {
        final float fromDegrees = mFromDegrees;
        float degrees = fromDegrees + ( ( mToDegrees - fromDegrees ) * interpolatedTime );

        final float centerX = mCenterX;
        final float centerY = mCenterY;
        final Camera camera = mCamera;

        final Matrix matrix = t.getMatrix();

        camera.save();
        if( mReverse )
        {
            camera.translate( 0.0f, 0.0f, mDepthZ * interpolatedTime );
        }
        else
        {
            camera.translate( 0.0f, 0.0f, mDepthZ * ( 1.0f - interpolatedTime ) );
        }
        camera.rotateY( degrees );
        camera.getMatrix( matrix );
        camera.restore();

        matrix.preTranslate( -centerX, -centerY );
        matrix.postTranslate( centerX, centerY );
    }
}
